EFFECTS OF SUSTAINED HIGH INTENSITY INTERVAL TRAINING (HIT) ON EXERCISE PERFORMANCE, SKELETAL MUSCLE & CARDIAC FUNCTION IN CARDIAC REHABILITATION PATIENTS 491

Abstract

This study compared the effects of the addition of a 10 wk HIT program of cycle ergometer training @ 80-90% of VO2max; (n=9) to continued conventional aerobic exercise @ 60-70% of VO2max (CONT;n=8), on maximal(MAX) and submaximal (SMX) exercise performance, skeletal muscle strength and resting cardiac function in 17 aerobically trained patients participating in a cardiac rehabilitation program. Before and after intervention both groups performed: i) graded exercise to exhaustion, for determination of VO2max and peak power output (PPO); ii) a 6 min walk test (6WT) for distance covered; iii) tests of isometric and isokinetic skeletal muscle function (SMF) & iv) echocardiography for determination of ejection fraction (EF) and left ventricular mass (LVM). At baseline, all parameters were similar between HIT and CONT groups. After intervention, PPO increased by 17% (130±12 vs. 156±12 W; [mean±SEM]; P<0.05) in the HIT group but was unchanged in the CONT group (140±14 vs. 136±14 W). Similarly VO2max increased 18% after HIT (24.5±1.9 vs 29.7±1.9; mlO2·kg·min-1; P<0.05) but was unchanged in the CONT group (23.3±2 vs. 24.2±2.3 mlO2·kg·min-1). Distance covered in the 6WT increased after HIT (11%; 635±27 vs. 713±27 m; P<0.01) but was unchanged in the CONT group (584±45 vs. 577±28 m). EF, LVM and SMF did not change in either HIT or CONT groups. These results suggest that HIT resulted in improved MAX and SMX exercise performance, which could not be attributed to enhanced resting cardiac function or SMF. These adaptations exceed those seen in the healthy athletic population performing HIT.